The present disclosure relates to a controller configured to control an internal combustion engine that includes an exhaust purification device, which purifies exhaust gas discharged from cylinders, fuel injection valves provided for the respective cylinders, and a crankshaft coupled to a multi-speed transmission.
For example, Japanese Laid-Open Patent Publication No. 2004-218541 discloses a controller that executes dither control. In the dither control, when there is a requirement for an increase in the temperature of a catalyst device (catalyst), the air-fuel ratio is made richer than the stoichiometric air-fuel ratio in some cylinders, while the air-fuel ratio is made leaner than the stoichiometric air-fuel ratio in the other cylinders.
Also, a controller has been known that variably controls the gear ratio of a multi-speed transmission connected to the crankshaft of an internal combustion engine.
When the dither control is executed, the rotational fluctuation of the crankshaft of the internal combustion engine tends to be larger than that when the dither control is prohibited. Therefore, when changing the gear ratio by operating the multi-speed transmission at the execution of the dither control, the controllability of the control of changing the gear ratio may deteriorate.